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Spawn model from robot_description topic

#gazebo   #ign   #spawn  

Table of Content

LAB#

Spawn sdf/xacro model into simulation using topic argument

  • using robot_description_publisher
launch/minimal_topic.launch.py
import os
from launch import LaunchDescription
from ament_index_python.packages import get_package_share_directory
from launch.actions import IncludeLaunchDescription, TimerAction, LogInfo
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch_ros.actions import Node

WORLD_NAME = "demo"
MODEL_NAME = "sam"

def generate_launch_description():
    package_name = "sam_bot_description"
    sdf_model_path = MODEL_NAME + "/model.sdf"
    world_file_path = WORLD_NAME + ".sdf"

    # Pose where we want to spawn the robot
    spawn_x_val = "-2.0"
    spawn_y_val = "0.0"
    spawn_z_val = "0.5"
    spawn_yaw_val = "0.0"

    pkg_ros_gz_sim = get_package_share_directory("ros_gz_sim")
    pkg_share = get_package_share_directory(package_name)
    world_path = os.path.join(pkg_share, "worlds", world_file_path)
    sdf_models_path = os.path.join(pkg_share, "models", sdf_model_path)

    robot_state_publisher = Node(
        package="robot_state_publisher",
        executable="robot_state_publisher",
        output="screen",
        parameters=[
            {"use_sim_time": True},
            {"robot_description": open(sdf_models_path).read()},
        ],
    )

    gazebo = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            os.path.join(pkg_ros_gz_sim, "launch", "gz_sim.launch.py")
        ),
        launch_arguments={"gz_args": f"-r {world_path}"}.items(),
    )


    spawn_entity_cmd = Node(
        package="ros_gz_sim",
        executable="create",
        arguments=[
            "-world",
            WORLD_NAME,
            "-topic",
            "robot_description",
            "-x",
            spawn_x_val,
            "-y",
            spawn_y_val,
            "-z",
            spawn_z_val,
            "-Y",
            spawn_yaw_val,
        ],
        output="screen",
    )

    timer = TimerAction(period=1.0,
            actions=[
                spawn_entity_cmd,
                LogInfo(msg="------- Spawn ------------")
                ])

    ld = LaunchDescription()
    ld.add_action(robot_state_publisher)
    ld.add_action(gazebo)
    ld.add_action(timer)
    return ld

LogInfo

Log to 

from launch.actions import LogInfo

LogInfo(msg="------- message ------------")

TimerAction

Start Node after period

from launch.actions import TimerAction

timer = TimerAction(period=1.0,
        actions=[
            Node
            LogInfo(msg="------- Spawn ------------")
            ])